Money is no laughing matter so making it a quest sounds fun but if they don't figure it out then you have wasted everyones time and your money would be gone forever.
I thought of this also but if you let the beneficiaries know the amount of "treasure"
they could hope to uncover and keep, well then im sure they would figure it out no
matter what and of course its not going to be impossibly difficult after all you want
those bitcoins found!